Mobile communication has been one of the most successful innovations in modern history. Recently, the number of subscribers to mobile communication services exceeded 5 billion and continues to grow quickly. At the same time, new mobile communication technologies are being developed to satisfy the increasing demand and to provide more and better mobile communication applications and services. Some examples of such systems are cdma2000 and 1xEV-DO systems developed by 3GPP2; WCDMA, HSPA, and LTE systems developed by 3GPP; and mobile WiMAX systems developed by IEEE. As more and more people become users of mobile communication systems, and more and more services are provided over these systems, there is an increasing need for mobile communication systems with larger capacity, higher throughput, lower latency, and better reliability.